The present invention relates to laminated safety glass glazing units of the type for security installations and for windshields of aircraft. More particularly, the present invention relates to a means for securing a laminated safety glass unit to a frame or other structural unit.
In detention and security facilities such as prisons, police stations, military compounds, banks, etc. transparent laminates having high resistance to impacts comprising at least one sheet of transparent plastic material interposed between sheets of glass or plastic material are being utilized in place of wall units or security bars. New types of plastics and glass have been developed for use in such laminates to prevent penetration by projectiles and/or various blunt instruments or devices. In this regard, there has been great advancement in preventing penetration of the protective structure by a direct attack on the laminate. However, little progress prior to the present invention has been made to overcome the breach of security through the removal of the laminate from the frame or structural member without directly attacking the laminate or to prevent delamination after the laminate has been fractured.
Windshields and canopies for aircraft have been constructed from laminates in order to withstand high energy impacts as by collision with a bird at high speeds. The laminates are usually mounted so as to transmit loads thereon directly to the frame of the aircraft. In a typical construction the outer plies are affixed to the airframe so that non-impact loads, for example, loads caused by pressurization, are also transmitted to the airframe. The securing of the laminates to the air frame whereby there is contact of the outplies with the metal of the aircraft or within the frame can cause stress cracks along the edges especially at low temperatures where elastomeric supports harden and shrink. Stress cracks can further occur by the use of bolt fasteners and clamping means directly on the out plies.
In both aircraft and security installations time is critical when the laminates are being subjected to stress and impact to prevent their complete removal from their frames or supporting structures. Merely bolting or clamping the laminates into a frame or supporting structure in some cases is not adequate to prevent their sudden removal after stress and impact and results in premature cracking along the peripheral areas even without the anticipated impact.